Modern radiation therapy techniques include the use of Intensity Modulated Radiotherapy (“IMRT”), typically by means of an external radiation treatment system, such as a linear accelerator, equipped with a multileaf collimator (“MLC”). Use of multileaf collimators in general, and an IMRT field in particular, allows the radiologist to treat a patient from a given direction of incidence to the target while varying the shape and dose of the radiation beam, thereby providing greatly enhanced ability to deliver radiation to a target within a treatment volume while avoiding excess irradiation of nearby healthy tissue. However, it is difficult to take full advantage of this greater freedom afforded by IMRT and other complex radiotherapy techniques, such as volumetric modulated arc therapy (VMAT, where the system gantry moves while radiation is delivered) and three-dimensional conformal radiotherapy (“3D conformal” or “3DCRT”).
For example, treatment plans can still provide too much radiation to organs at risk. Some techniques take into consideration the maximum resolution of the MLC based on physical dimensions of the individual leaves. For instance, the width of a leaf limits the precision with which a radiation dose can be delivered through an aperture formed by the leaves. However, conventional techniques fail to take into account the various ways in which leaf geometry contributes to unwanted radiation, i.e., more radiation than desired or radiation delivered to areas that should be left untreated.